I'm going to go ahead and recomend The Wheel of Time series for fantasy books, epic in everyway.
For Sci-Fi I would have to recomend Enders Game, about a child being whisked away at the age of mearly three to attend an unforgiving school where children are trained to meet an alien menace.
Two more for 'ya, though they may be a bit more Horror than they are Sci-Fi:
Plague Zone [http://www.brokentype.com/pz/] As you probably guessed, about a zombie plague.
Thirteen Bullets [http://www.brokentype.com/thirteenbullets/2006/01/1.html] This ones the first in a series of gruesome vampire hunting tales. It's a bit different, as the vampires within arn't the civilized almost nobel quiet vampires, rather they are brutal blood crazed killers. Oh! And no Vampire on Human love, which I don't know about you, but is a major plus for me.
By the way, First Post for me, Huzzah!
EDIT: Forgot to mention that if you follow the Thirteen Bullets and Plague Zone links you can read 'em online.